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Subject: Plant Pathology × Author: KAU × End date: 1984 × Start date: 1984 ×
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    ThesisItemOpen Access
    Varietal screening of banana against anthracnose disease
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1984) Srinagesh, K L; KAU; Jose, P C
    Laboratory and field studies of the varietal screening of banana against anthracnose disease were conducted at the college of Horticulture. Vellanikkara and at Banana Research Station, Kannara respectively during 1981-1983. In the field the infection started at the distal end of the banana fruit and in course of time the infected fruit became blackened, shriveled and mummified. After Harvest, the symptoms appeared as small brown spots which enlarged quickly and coalesced forming larger patches. The affected areas were covered with orange to salmon pink coloured conidial masses. The detailed morphological studies of the fungus proved that the anthraemose disease of banana is caused by colletrichum cloeosporioides cooko and massee, the imperfect stage of glomerella cinoulata spauld and shrenk. Twenty five varieties of banana fruit were screened in vitro at different stages of development against anthracnose disease. The varieties showed different degrees of susceptibility at various developmental stages of the fruit. The pooled analysis of the data showed that the variety nendra padaththi followed by palayankodan, jurmani kunthali, boodida bontha bathes, peyan, kanchikela, pisang mas and kapok were found to be highly resistant. The varieties Zanzibar, adakka kunnan, klue teparod, chinia, nendran, venneettu mannan, koduppilla kunnan, hybrid sawai, poocha kunnan, red banana and boodles altafort were found to be resistant to the disease. The variety robusta was found to be susceptible. The varieties njalipoovan, pisang lilin, dwarf Cavendish, matti and gros Michel were found to be highly susceptible. The major chemical constituents of banana fruit viz. reducing sugars, total sugars starch, crude fibre, crude protein and tannin at different developmental stages of twenty five varieties were analysed. The reducing sugars and total sugar were found to increase steadily from immediately after female phase to ripened stage in all the varieties. The starch and crude fibre contents, though increased steadily upto full maturity. Declined sharply at the ripening stage. The crude protein and tannin contents were maximum at immediately after female phase but steadily decreased and were minimum at ripening phase. There was a significant positive correlation between reducing sugars, total sugars and per cent disease intensity at three fourth maturity. High sugars were responsible for susceptibility to the disease. A significant negative correlation was obtained between crude protein and per cent disease intensity at half maturity. A significant negative correlation was also obtained between tannin and per cent disease intensity at one fourth and half maturity stages. High crude protein and high tannin contents were responsible for resistance to the disease.
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    ThesisItemOpen Access
    Evaluation of various herbicides on the control of sheath blight disease (Rhizootonia solani Kuhn) on rice
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1984) Lakshmy, T R; KAU; Chandrasekharan Nair, M
    Both in vitro and in vivo studies on the effect of few common herbicides on Rhizoctonia solani and on sheath blight of rice, were carried out. The in vitro studies revealed that Propanil (Stam P.34) vras the most toxic herbicide to Rhizoctonia solani Kuhn, the rice sheath blight pathogen, which completely inhibited nycelial growth at a very low concentration of 125 ppm. Benthiocarb, Nitrofen (Tok E.25) and Butachlor also have high potentiality in decreasing radial growth and also in inhibiting the formation of sclerotia Soil borne sclerotia was found the major source of inoculam in initiating sheath blight diseases. Among the various herbicides tested, Nitrofen, Propanil and Butachlor reduced the degree of pathogenicity of soil borne sclerotia of R. solani* Propanil effected maximum reduction of sheath blight in pot culture experiments followed by Nitrofen. Butachlor and Nitrofen were equally effective in reducing sheath blight under pot culture, experiment. Nitrofen (Tok E.25) applied at 1.5 kg ai, 1.75 leg ai were equally effective as Hinosan in reducing sheath blight in field trial also.
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    ThesisItemOpen Access
    Yellow vein mosaic disease of pumpkin in Kerala
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1984) Jayasree, P K; KAU; Balakrishnan, S
    Yellow vein mosaic disease of pumpkin ( Cucurbita moschata Dutch. ex Poir) caused by a virus, was investigated which was prevalent in Vellayanl and nearby localities. The symptoms appeared as faint yellowing of finer veins which later on develop into characteristic vein yellowing. In advanced stages of infection, chlorotic areas were seen on the leaf lamina along with vein yellowing symptoms. The size of the leaves was reduced markedly.The growth of infected plants was severely retarded. The infected plants produced less female flowers and when Infected at a later stage produced undersized fruits. Histopathological studies showed a reduction in thickness of the chlorotic portions of the infected leaves and the palisade cells were shortened and loosely packed. The mesophyll cells contained only few chloroplasts. The virus was not sap transnissible. But it could be transnitted through grafting* The virus was hot found to be transmitted through seeds.
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    ThesisItemOpen Access
    Studies on leaf curl disease of sesamum
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1984) Jayasree, M; KAU; Balakrishnan, S
    Leaf curl disease of sesamum, its symptomatology, mode of transmission, vector-virus relationships, the pattern of spread under field conditions and the extent of loss caused by the disease were investigated. Major symptoms of the disease were abaxial curling of the leaves, thickening of the veins on the under surface of the leaves, leathery appearance of the leaves and reduction in the size of leaf lamina. The plants remained stunted and produced few flowers and pods when infection occurred during the early stages of the plant growth. When infection occurred during later stages there was production of flowers and pods hut to a limited extent. This particular virus could he transmitted by wedge and side grafting and by the whitefly Bemisia tabaci Genn. The minimum, acquisition feeding period was found to be 10 min and the minimum inoculation feeding period was 20 min. The vector required an incubation period of 28 h to become viruliferous. Even a single whitefly was found to be capable of transmitting the virus. Once the vector acquired the virus it would retain it till its death. Negative results were obtained in the case of sap and seed transmission showing that this particular virus was not sap and seed transmissible.